1. Technical Field
The present invention relates to lead frames typically used with packaged integrated circuits, and more particularly to the tie-bar portion of the lead frames wherein the tie-bar includes a non-conductive portion for use in the production and/or testing of microcircuits.
2. Background Information
Typically, as is known in the art that integrated circuits and microcircuits, such as transistor-transistor logic (TTL), emitter-coupled logic (ECL), hybrid circuits, and the like, are hermetically sealed either in flat packages, such a T- or W-type, or in dual-in-line packages, such as ceramic or plastic. See e.g., Texas Instruments, Inc., The TTL Data Book For Design Engineers .sctn. 4 (2d ed. 1981). In order to electrically contact the packaged microcircuit from the exterior of the package, metallized leads are integrated into the package to provide an electrically conductive path to the circuit.
Examples of the lead frame and packaged metallized leads are shown with references to FIGS. 1 through 3. In FIG. 1, a typical metallized lead frame 10 for use in an integrated circuit package is shown, wherein leads 11 are attached to tie-bar 12. The tie-bar typically has at least one hole 13, allowing the lead frame to be secured while leads 11 are attached to a package body. In FIG. 2, a typical metal integrated circuit package is shown with dual lead frames 21a and 21b extending through two opposite sides of package body 22. In FIG. 3, a typical ceramic microcircuit package is shown with dual lead frames 31a and 31b attached to package body 32. The package leads are typically made of KOVAR.RTM. (military specification F-15), 42 alloy, or other similar materials.
As is well known in the art, the tips of the leads of the lead frame used in a metal integrated circuit package serve as the bonding pads on the interior of the package. In a ceramic package, the tips of the leads are attached to a metallized path which extends from the package interior to its exterior.
After a package is manufactured, the metal portions of the package are typically plated to protect against corrosion. Additionally, the lead frames are plated with an easily weldable, solderable, or bondable material, such as gold or silver, for aiding in attachment to the pads and soldering or welding to the leads. The platings are most typically applied electrically. To allow all leads on the tie-bar to be electroplated at the same time, the tie-bar remains attached to the adjoining leads, thereby providing electrical contact to all respective leads.
After electroplating the leads, the microcircuit is inserted and wire bound to the package's bonding pads. Typically, tests are conducted on the microcircuit, especially when a new design is being developed. To test the circuit, the electrically-conductive tie-bar must be removed. During the manufacture of a new microcircuit design, such as a hybrid microcircuit, the device is often tested repeatedly, with repairs and/or modifications made while testing and troubleshooting. Tests are performed typically after every phase of completion. For example, conductivity testing is done during the assembly, and dynamic testing is done at the completion of the integrated circuit. The leads on these microcircuit packages are typically 0.010 inches thick and 0.015 inches wide. Accordingly, they are highly fragile and bend easily. Repeated minor bending of the lead often causes breakage.
A broken lead causes many problems. Many specifications limit the number of times that a microcircuit, such as a hybrid, can be repaired. Additionally, transferring the circuit from one package to another is either against specifications or impractical due to the number of wire bonds that are involved.